Articulated vehicles are well-known, and generally include a tractor and a trailer, the trailer being secured to the tractor such that the two may pivot relative to one another about the point of connection. The tractor provides the means for driving the tractor and trailer combination, and is typically the steering means for the combination. In a ‘double combination’ vehicle, a second trailer is typically towed by a dolly attached to the back of the first trailer and is the steering means for the second trailer such that the two may pivot relative to one another about the point of connection. However, the prior art does provide for trailers that provide a counter-steering function.
For example, in U.S. Pat. No. 7,793,965, apparatus and methods are provided for measuring the angle of articulation between a tractor and trailer so that the wheels of the trailer can be counter-steered to better track the movement of the tractor. The counter-steering of the trailer wheels is dependent upon an articulation angle measurement, and the present invention serves to provide improvements in apparatus designed to measure such an angle of articulation.